The present invention relates to a cord lock for a venetian blind lift cord.
Many forms of such lock have been proposed. In one simple arrangement the lift cord is locked between a fixed member and a locking roller, the locking roller being capable of sliding along a guide slot in the vertical direction under the action of the upwardly moving cord. The cord is thus clamped between the fixed surface and the locking roller.
In mounting such a construction in the headrail of a venetian blind, great care has to be taken to ensure that the lock is positioned the right way round depending on whether the lift cord is at the lefthand or righthand end of the head rail.
It is now proposed, according to the present invention, to provide a cord lock for a venetian blind lift cord, said cord lock comprising, in combination:
(a) front and rear plates maintained generally parallel to one another;
(b) a guide roller mounted between said front and rear plates, with its axis extending substantially normal to the front and rear plates;
(c) guide slots formed in the front and rear plates in register with one another, the guide slots including:
(i) side arms which are inclined towards one another in an upward direction, the axes of the side arms extending one on each side of the axis of the guide roller; and PA1 (ii) a cross arm joining the side arms and extending below the guide roller;
(d) a rotatable locking roller having end shaft portions mounted in the corresponding side arm of each guide slot and movable in the axial direction of the side arms in which they are mounted, effective to enable a cord passing around the guide roller and between the guide roller and locking roller to be releasably locked therebetween, the dimensions of the cross arms and locking roller shaft portions being such as to allow forceable movement only of the locking roller from one side arm to the other.
With such a construction, the locking roller is normally slidable in one of the side arms of each guide slot to carry out its locking action. If one wishes to mount the same lock at the other end of the blind, then the locking roller is simply forced through the cross arm to the other side arm of each slot. This is not normally possible during use of the cord lock. Thus, the supplier only has to stock one form of cord lock and this can be used at either end of the venetian blind headrail.
Preferably the guide roller and locking roller are dimensioned such that, when the locking roller is located at the lower end of the corresponding side arms of the guide slots, the free hanging cord, when moving upwardly, will itself engage and lock the locking roller. This can be achieved by making the dimensions of the guide roller and locking roller such that the nearest portion of the surface of the locking roller is spaced from the vertical plane including the axis of the guide roller by a distance about equal to the radius of the guide roller.
In order to facilitate the introduction of the guide roller into the lock, the rear wall advantageously extends upwardly beyond the front wall and an aperture is formed in the front wall with an elongate slot having its axis extending vertically being provided in the rear wall, the elongate slot also extending upwardly beyond the front wall. The elongate slot has a lower end in register with the aperture, so that the aperture and the slot can each receive a shaft end portion of the guide roller. In the assembly operation, the rear shaft portion of the guide roller is inserted in the upper end of the slot, and the front plate is pulled forwardly and the guide roller allowed to move downwardly until the forward shaft portion can be engaged in the aperture.
To facilitate the introduction of the lock into the headrail of a venetian blind, the rear wall preferably extends upwardly beyond the front wall and a rearwardly extending locking surface is provided adjacent the upper end of the rear wall to engage under the rim of the rear flange of a venetian blind headrail, a forwardly projecting tab on the front wall, adjacent the lower end thereof, being provided to engage in an aperture in the front wall of the headrail, the locking surface comprising a curved portion enabling the locking surface to engage under the rim by snap-in action upon pivoting of the lock about the tab.
According to a further aspect of the invention, there is provided a cord lock for a venetian blind lift cord, said cord lock comprising, in combination:
(a) front and back plates;
(b) cord locking means mounted between said front and back plates;
(c) a tab extending transverse to the front and back plates adjacent each side thereof;
(d) a correspondingly shaped curved edge surface on each tab;
(e) aligned pivot forming recesses in the edges of said tabs;
(f) aligned locking recesses in the edges of said tabs at a location spaced along the curved edge from the associated pivot forming recess; and
(g) a resilient wire separator, for separating lift cords from one another, said separator including a pivot portion engaged in the pivot forming recess and a locking portion slidable over the curved edge surface, upon pivoting of the separator about the pivot portion, whereby the locking portion can be resiliently engaged in said locking recess.
With such a construction the wire separator, which is used to separate two or more lift cords from one another, is housed completely within the headrail and is therefore kept out of view. The method of mounting is extremely simple and inexpensive.
In order that the present invention may more readily be understood, the following description is given of a presently considered preferred mode of putting the invention into effect, reference being made to the accompanying drawings.